The present invention generally relates to a haptic gaming device, and more specifically, to a power supply for a haptic feedback gaming device, such as a force-feedback joystick.
Electronic devices used with conventional personal computers (PCs) are typically energized through a connection to a port on the PC, or by using batteries, or by connection to an alternating current (AC) line power source. Battery power supplies are generally less desirable for devices that consume more than a few milliwatts of power, due to the size of the battery supply required for continuously energizing the device and because of the cost and inconvenience associated with charging or replacing batteries. If such an electronic device is relatively small and compact, it is common practice to supply the required electrical current from a power supply module (commonly referred to as a xe2x80x9cpower brickxe2x80x9d) that directly plugs into an AC wall outlet. If the power brick is too large to conveniently and directly plug into an AC outlet, a short line cord may be provided to connect the power brick to the outlet. The output current from the power brick, which is typically a direct current (DC), is then connected to the electronic device through a small gauge cable. By using this type of power source, the power transformer and other components typically employed for a power supply need not be included in the electronic device. The electronic device can thus be smaller and more portable than would be the case if the power supply were integrally included in the device. In many cases, it would simply not be possible to include the components used in a power supply integrally within the electronic device because of size and weight limitations.
Haptic gaming devices, such as force feedback joysticks and force feedback wheels, are examples of one type of electronic device that is normally energized with an electrical current provided by a power brick. A force feedback joystick typically includes a control handle that is pivotally mounted to a base so as to enable motion in at least two orthogonal directions. Included within a housing of the joystick is at least one electric motor that must be energized with an electrical current to provide the force feedback response. The power requirement for the electrical motors used in these devices is normally too great to supply from a port (RS-232 serial port, parallel port, game port, or universal serial bus (USB) port) of a PC and must instead be supplied by a separate power supply that is connected to an AC line. Furthermore, due to the need to minimize the size of the base of a force feedback joystick, and the need to insure that it is relatively lightweight and portable, since a user frequently picks up the joystick and moves it about during game play, all force feedback joysticks known in the prior art have obtained the electrical current needed to energize the force feedback motors from an external power brick that is connected to the AC line.
It has generally been held that the required electrical current for energizing force feedback motors in a haptic gaming device is too great to be supplied from an integral power supply disposed within the housing of the device. The size and weight of the components used in a typical power supply, if included within the housing of a haptic gaming device such as a joystick, would indeed cause it to be unacceptably large and heavy. While other types of power supplies that are capable of supplying the required current and are smaller in volume than a conventional power brick are known in the prior art, such power supplies have generally been considered to be too expensive for use in a consumer haptic gaming device, since it is important to minimize the cost of such devices to remain viable in a competitive market.
Newer haptic gaming devices require even more electrical power to improve the response of the electrical motors to force feedback commands. Providing the increased power from a conventional power brick that plugs directly into an AC outlet is not practical due to the greater size of components such as the transformer that would be required to provide the power. Also, it is desirable to reduce the overall weight of the haptic gaming device and all of its associated components, such as the power supply, to minimize shipping costs of the product in the distribution network. Accordingly, a different type of power supply is required that is low in cost, uses relatively few parts, and is very compact. Ideally, the power supply should be integral with the haptic gaming device to eliminate the need for a separate modular power supply component, and the weight and volume associated with packaging and shipping such a component with the force feedback joystick or other haptic gaming device. Currently, there are no haptic gaming devices that include an integral power supply meeting these requirements.
In accord with the present invention, a haptic gaming device is defined that includes a housing in which is disposed a prime mover used to produce a force feedback. Disposed within the housing is a control for the prime mover and an integral power supply for the prime mover. The integral power supply, which is adapted to couple to an alternating current (AC) line power source, provides power to the prime mover to energize it.
The power supply includes a rectifier that converts the AC line power to a direct current (DC) voltage. A transformer in the power supply is coupled to the rectifier to receive the DC voltage, and an electronic switching circuit is included to respond to a feedback signal produced by the transformer and to periodically connect the rectifier to the transformer so that the transformer is supplied with a pulsed DC voltage.
The transformer preferably includes two primary windings and a secondary winding. One of the primary windings provides the feedback signal for controlling the electronic switching circuit and the other primary winding is energized by the pulsed DC voltage. The electronic switching circuit also preferably comprises a pulse width modulator (PWM) switching control that periodically interrupts the DC voltage applied from the rectifier to the transformer at a predetermined frequency and varies a duty cycle of the pulsed DC voltage thus produced to maintain an output voltage on the secondary winding of the transformer within a predetermined range. This output voltage is coupled to the prime mover, to energize it. In a preferred embodiment of the present invention, the PWM switching control maintains the output voltage of the transformer within the predetermined range for an input AC line voltage that varies by more than 100 volts.